SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21cea657d2a386770a7bceceba8b5f9992e65779bde3069c94949dd49345021f' 
  AND token = '1lbK1GB47tizQ76w0v6J9CkTKFR7wlpZ3w/8hSShQrg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}